Terminal Part of Thoracic Duct: High-Resolution US Imaging

Abstract

PURPOSE: To assess ultrasonographic (US) examination results of the cervical part of the thoracic duct, to provide standard diameters, and to evaluate the diameter of the cervical thoracic duct in certain diseases suspected to involve an abnormal load of chyle (liver, heart, and inflammatory bowel diseases). MATERIALS AND METHODS: The study was approved by the institutional review committee, and written informed consent was obtained from all subjects. Diameter and variations of the cervical thoracic duct were assessed by using US in 265 healthy volunteers (age range, 21-82 years) from a population-based study, in 196 subjects with documented liver cirrhosis (age range, 19-87 years), in 68 subjects with chronic hepatitis (age range, 17-73 years), in 39 subjects with congestive heart failure (age range, 46-85 years), and in 17 subjects with inflammatory bowel disease (age range, 18-66 years). US examinations were performed with high-resolution linear probes (7-12 MHz). RESULTS: A standard imaging approach guided by anatomic structures was established. Dynamic imaging of the chyle flow and valve function was possible. The thoracic duct was visualized in 564 (96%) of 585 examinations. The average thoracic duct diameter in healthy volunteers was 2.5 mm, which was independent of the subjects' age. The diameter was significantly higher in subjects with congestive heart failure (6.3 mm, P < .0001) and liver cirrhosis (5.6 mm, P < .0001). Anatomic variations were present in 27% of subjects. CONCLUSION: High-resolution US with linear probes allows assessment of the cervical thoracic duct with high detection rates. Recognition of local anatomy, diameter, and chyle flow may aid functional assessment.